1. Field of the Invention
The present invention relates to a nonvolatile memory device, and more particularly, to a nonvolatile memory device having twin memory cells.
2. Description of the Related Art
Nonvolatile memory devices using resistance materials include Resistive Random Access Memory (RRAM), Phase-change RAM (PRAM), and Magnetic RAM (MRAM). Dynamic RAM (DRAM) and flash memory devices store data using charges. Nonvolatile memory devices using resistance materials may store data using the resistance change of variable resistive elements (for example, RRAM), phase change of phase change materials, such as chalcogenide alloy (for example, PRAM), and resistance change of Magnetic Tunnel Junction (MTJ) thin films according to the magnetization state of a ferromagnetic substance.
More particularly, a resistance memory cell includes a variable resistive element between an upper electrode and a lower electrode, and the resistance level of the variable resistive element may be changed according to a voltage supplied to the upper and lower electrodes. The state where the variable resistive element has a high resistance is defined as high resistance data, which is reset data (1), and the state where the variable resistive element has a low resistance is defined as low resistance data, which is set data (0).